Hydrothermal Explosion Hazards at Crater Lake

In the right conditions, when magma or hot rocks encounter water hydrothermal explosions can
occur. This could happen if magma encounters water from Crater Lake itself or ground water.
These types of eruptions may eject large ballistic blocks (tens or more centimeters in diameter) to
distances up to a few kilometers. At Crater Lake, blocks ejected at a couple hundred meters per
second (typical velocity) could travel a few kilometers (a couple miles), and could easily overtop the
caldera rim if the eruption vent were near the lake's shore. Hydrothermal explosions could also
cause water waves on the surface of the lake up to a few meters in height, which would be very
hazardous to people on the lake's surface or shorelines.